Amy Siewert, a firearms expert with the Florida Department of Law Enforcement, faces the jury as she demonstrates George Zimmerman's gun during the George Zimmerman trial in Seminole circuit court, in Sanford, Fla., Wednesday, July 3, 2013. Zimmerman is charged with second-degree murder in the fatal shooting of Trayvon Martin, an unarmed teen, in 2012. (AP Photo/Orlando Sentinel, Jacob Langston, Pool)— AP

Amy Siewert, a firearms expert with the Florida Department of Law Enforcement, faces the jury as she demonstrates George Zimmerman's gun during the George Zimmerman trial in Seminole circuit court, in Sanford, Fla., Wednesday, July 3, 2013. Zimmerman is charged with second-degree murder in the fatal shooting of Trayvon Martin, an unarmed teen, in 2012. (AP Photo/Orlando Sentinel, Jacob Langston, Pool)
/ AP

SANFORD, Fla. 
Two weeks and about three dozen witnesses later, prosecutors are about to rest their case in George Zimmerman's second-degree murder trial in central Florida.

The prosecution was expected to wrap up their questioning of witnesses Friday - although they still may call Trayvon Martin's parents to testify. The parents have said it's their 17-year-old son screaming for help on 911 calls recorded during a fight the unarmed teen had with Zimmerman, a neighborhood watch volunteer, last year before Zimmerman fatally shot him.

Zimmerman's father has said it is his son. The screams are crucial pieces of evidence because they could determine who the aggressor was in the confrontation.

Zimmerman's attorneys will start their case after the prosecution rests.